Tuesday, December 28, 2010

I've been thinking about languages a lot lately. Which is kind of a joke, given the title of my blog, but I actually mean "I've been thinking about them more than usual". This thought has been specifically dominated by thoughts of the Blub hierarchy as proposed by Paul Graham.

I'm not sure what's on top.

PG claims "Lisp", I've seen many that shout "Ruby", I've met many that claim "Haskell". In fact, if you participate in programming discussion for any length of time, there's a pretty good chance that you'll meet someone for every language (other than C) claiming it's Omega. It's ridiculous, of course. All most of them are really claiming is "This is the most powerful language I know how to work with", which is not the same thing as "the most powerful language". It's easy to see that trying to compare in any supposedly objective sense would cause giant hatestorms and various infighting. So people are perhaps justified in making statements like

"You don't compare a hammer with a screwdriver, but you use the one that fits your task & way of thinking/education/needed level of abstraction the most. Also, since the one doing the comparison is biased by the fact that he knows at least one of the two, or at least prefers one of the two, it is hard to find a truly objective criteria for comparing them (exceptions exist)." -Rook, pogrammers.SE

when discussing language comparison. That was an answer from a question about whether language comparison was useful. As of this writing, it has been closed and re-opened twice, and the original asker has accepted (then unaccepted, then accepted again) a joke answer. This is perhaps more telling of the culture of programmers.SE than of the question, but it doesn't seem like an uncommon response. People duck comparisons precisely because languages are half tools and half religions, and no one wants a crusade declared. But, well, you need to compare.

"A language is a tool. That said, I've seen really, really crappy tools before. No one wants to work with a hammer whose head is liable to fly off and hit another carpenter in the stomach. Likewise, if you noticed your fellow worker's hammer was in that shape, you'd probably steer clear of them when they were using it. It's also important to really understand which tool it is. You can't use a screwdriver and hammer interchangeably (though some try desperately). Hell you can't even use all hammers interchangeably; you need a sledge for some things, a mallet for others and a tack for yet others. If you use the inappropriate tool, then at best, you'll do a poorer job, at worst you'll injure yourself or a co-worker." -me, programmers.SE

Graham goes further, stating that not only can you compare languages in terms of power, but goes on to point out the obvious corollary that there is therefore such a thing as an empirically best language. As a note, I agree with him, but "which religion is best?" is a question you just don't discuss in polite society, so I haven't pushed the idea on any forum I frequent. It makes sense though. No one would disagree that Assembly < Cobol < Python on the power scale (I'm defining "power" as a non-specific mix of expressiveness, terseness, maintainability, readability and flexibility). And even admitting that simple truth exposes you to the idea that there's a ladder, or tree, or at least concentric circles of languages with one (or a relatively small group) taking the prime position.

Omega.

Graham puts Lisp there, but he's making the same claim that any Ruby ardent or avid Haskeller are expressing; "Of all the languages I know, this one is the most powerful". The thing is, I haven't heard many convincing arguments to the contrary. The best argument aimed at Lisp these days is that it's slow, and even then, slow in what sense? It can certainly do the job of server software, or even local desktop/console software on today's powerful systems. Remember, Lisp was called slow back when 1Gz was the sort of processing power you paid many thousands of dollars for. I have more than that right now in my $300 dollar netbook. We're fast approaching an age where a phone you get for free with a subscription is more powerful. "Slow" just isn't a good enough strike against a language to discount it anymore. Other than that, people complain about the parentheses, which is an empty complaint at best, and typically a trolling attempt. The only good argument against Lisp as Omega comes from an unlikely source.

"I don't think it's necessarily Omega. The Haskellers and MLers say 'Well, from where we sit, Common Lisp looks like Blub. You just don't understand the brilliance of strong inferred typing'. And they may be right. Of course, Common Lispers look at Haskell and say 'Well, Haskell's really Blub, because you guys don't have macros'. It may be the case that there is no Omega, or that Common Lisp and Haskell are on different branches of the lattice, and someone's gonna find a way to unify them and a few other good ideas and make Omega." -Peter Seibel, Practical Common Lisp Talk at Google

It's an interesting fact that practitioners of either language can point to lack of features in the other. That has some pretty obvious corollaries as well.

There may be such a thing as the most powerful language right now, but it may involve trade-offs (I don't know what it is, but one exists. I'll call it "Alpha" so as not to offend anyone).

There is such a thing as the language that will be the best for the next 10 to 100 years (This one may or may not exist in some form today; it might be unified from several current languages as Seibel alludes. I'll use his name and call it "Omega").

There is such a thing as the most powerful language that could exist on current machine architectures (This one almost certainly doesn't exist yet, and may never be embodied in an implementation. It's just the limit, in the calculus sense, of what we can hope to achieve with a language along the axes of expressiveness, terseness, maintainability, readability and flexibility. This one I'll call 0).

I'm not sure what Alpha is. I'm not sure anyone knows, because as I've said, people tend to bind that variable to whichever is the most powerful language they currently know. 0 is far away, and I won't even try talking about it today, because I don't have anywhere near enough information to make a decent guess at what it'll look like. So what does Omega look like? Well, Graham effectively says it's Arc (or what Arc will evolve into). Others variously substitute their own languages. There's a sizable community which thinks it's Haskell. Some ardents think it's Lisp. A few would like you to believe it's Java, despite the recent turbulence between Oracle and Google. And there are a couple of personalities in the industry who are vigorously pushing either Ruby or C#. Yegge echoes Seibel pretty closely

"[T]he Wizard will typically write in one of the super-succinct, "folding languages" they've developed on campus, usually a Lisp or Haskell derivative." -Steve Yegge, Wizard School

It's a line from one of his humorous, fictional pieces wherein he describes a Hogwart's-like school that churns out wonder-kid programmers, but it still seems like a vote for the Haskell/Common Lisp unification theory. It might happen. If it does, it'll be a race between the Haskellers and Lispers to out-evolve one another. In order to converge, Haskell needs to strap on prefix notation and macros, make IO easy (rather than possible), and blur the line between run-time, read-time and compile-time. Lisp needs declarative matching definitions, lazyness, currying (possibly eliminating the separate function namespace), strong types and a few small syntactic constructs (function composition and list destructuring leap to mind first). Lisp has a longer list to run through, but keep in mind that because it has macros, almost all of them can theoretically be added by you as you need them, rather than by CL compiler writers as they decide it's worth it.

It's also worth noting that the last point in Haskell's list is a pretty tricky proposition. How do you blur read/compile/run time when one of your goals is to have a complete type system? Well. REPLs for Haskell exist, so I assume it's possible, but making it part of the language core doesn't seem to be a priority at the moment (and probably won't be for a while due to the performance hits it imposes, and the perception performance hits still have in the general public of programmers). That's not the only hard bit either language would have though. How do you implement full currying and optional/default/keyword/rest arguments? Haskell purports to solve the problem by defaulting to currying, and giving you the option of passing a hash-table (basically) as an argument to implement flexibility. LISP gives you &rest, &body&key and very simple default argument declaration, but "solves" the currying issue by making currying explicit. Neither language's solution satisfies, because sometimes you want flexible arguments (and counter-arguing by saying "well, if you need them, you've factored your application wrong" is missing the point; expressiveness is a measure of power, remember, and having to think about the world in a particular way is a strike against you in that sense), and sometimes you want implicit currying (this is perhaps most obvious when writing in Haskell's point-free style, and if you've never done so, I doubt I could convince you).

As a common lisper, there are a bunch of things I'd like to steal from Haskell, if I could. The pattern-matching definitions are certainly useful in some places, list destructuring would help, and function composition seems useful (though this is, like defmacro, the sort of construct you have to understand first, in order to find places that it would greatly simplify). I'll check later, but I have a sneaking suspicion that someone has already lifted all of the above into a library somewhere on github or savannah. Even if not, list destructuring and function composition seem like they'd be easy enough to implement. The latter as a call to destructuring-bind, the former as a simple fold macro.

From the other side, there's already two projects underway; Liskell is a competing compiler to GHC that has a prefix notation and outputs the same machine code, and Lisk is a pre-processor for GHC that takes specific prefix notation forms and converts them programatically back to the Haskell source code before invoking the compiler. Lisk's creator talked briefly about macros, but the project is early enough along that nothing much more specific is out there right now (I'm watching his github repo with interest though).

I haven't a clue how to place my own bet. I tried starting this paragraph both with "My bet's on Lisp..." and "My bet's on Haskell...", but each beginning got to a logical dead end within two sentences. It doesn't seem like one can completely absorb the other. But, if Haskell + Lisp makes Omega, we'll see what it looks like shortly (by which I mean ~10 years) because cross-pollination is already happening, and it's not a far jump from there to full-on unification. Or maybe things get bloodier as the preview to Barski's Land of Lisp implies, who knows.

Either way, we'll see soon enough.

EDIT: rocketnia posted a particularly thoughtful response to the above post at the Arc Forum. He points out that there may not be an Alpha, Omega and 0, but rather "[L]ocal optima that can't be unified into Omega". I could have sworn I addressed this point (and acknowledged it, but stated that I was more interested the unification idea today), but my only mention of it is "...with one (or a relatively small group) taking the prime position." Apologies. He also explains a lot about how macros might coexist with a strong type system.

Tuesday, December 21, 2010

Just a quick update this week; I intend to record my thoughts on Bluetile (and I guess possibly xmonad by extension, but I get the feeling you could hammer the latter into a workable solution).

To start with

Why a Tiling WM?

I actually get asked this at work, so I won't assume that you're automatically on-board with the idea of using a tiling window manager. The most common questions are "Why?" and "Isn't it hard learning all those keystrokes?" The second is the easier question, so I'll answer it first; yes. But a good window manager should let you adjust keybindings[1], and the point here is to make your environment fast, not so easy to learn that the office secretary could use your computer in a pinch.

The answer to the first question is basically that.

It makes you faster.

Think about your editor. Actually, if you don't use Emacs, think about your editor. If you use Emacs, you already know what I'm talking about here; just skip to the next heading, where I give you the lowdown on Bluetile. Think about how you use that editor. Do you grab your mouse, and head over to the file menu every time you need to copy and paste something, or do you just Ctrl-c Ctrl-v? I'm hoping this is a ridiculous question; of course you use the keyboard shortcut when you can. It's faster. It would be utterly ridiculous to have to do everything with the mouse. Well, that's basically why. When you realize that the keyboard is so much faster, following that thread to its conclusion tells you that, except in special circumstances[2], you should use the keyboard as your primary input peripheral. If you analyze your mousing actions on a day-to-day basis, it'll occur to you that you spend a lot of time in a few different ways.

Browsing the net (where you use the mouse to click on links and right-click on various things).

Running programs (either from the dock on OS X or from the Start menu/desktop icons on Linux/Windows)

Moving, sizing and adjusting windows (especially if you've got multiple, large screens. I typically have my editor, browser, debugger, a terminal window and maybe a movie to watch in the background. As I type this, I'm watching a talk on "Models and Theories" by Peter Norvig, which I can heartily recommend.)

The first point is something that you'd want a keyboard-driven browser for (I use Conkeror for preference, though most people seem to have decided to live with the mouse in the context of their browser), but 2 and 3 are both things that a good tiling window manager will solve for you. Depending on the manager, you either get a "run" command (a keystroke that brings up a little input where you can type the name of the program you want to run), or a keystroke for the most common programs, or both, which means that you don't need to rely on the mouse to run programs. You just need to hit Win-p and type emacs or (in my case) hit C-t C-e. Either of these is faster than grabbing the mouse, getting to your desktop, moving the cursor over and double-clicking on the Emacs icon.

Moving, sizing and adjusting is typically done in order to get maximum use of your screen real-estate. For my part, I rarely want overlapping windows, but I always want as much of my screen used as possible. The way tiling WMs work is by automatically laying out any windows you open so that they take up as much space as you need (either by letting you specify splits and groups as in StumpWM, or by letting you manage layouts in xmonad). By remembering a few extra keystrokes, you free yourself entirely from the mouse.

So that's why.

Bluetile (really)

That brings me to Bluetile. I've been using StumpWM for my purposes, but I wanted to try out the competition. Bluetile is a derivative of xmonad, the Haskell-based tiling WM, with an aim of being easy for beginners to get into. They do this, kind of ironically, by putting in mouse-oriented controls and by running on top of Gnome instead of standalone. That's pretty sweet, actually, and it seems to be fairly easy for beginners to get into. The trouble is that it doesn't do a very good job solving the problems I mentioned above (so while it's easy to get into, I doubt it would do a good job convincing beginners that tiling WMs are worth the trouble). First, it provides on-screen icons for navigation (each of which have keyboard counterparts, I'm just bemoaning the waste of screen space), and it keeps toolbars and gaps between windows so that you can still see your start bar and background. The gaps have no reason I can see; the toolbars are kept so that you can still click on windows and drag them around, which sort of defeats the purpose.

That's all nitpicks though, and you could argue that beginners would find it easier than the full-keyboard control of something like the standard xmonad or Stump. The big downside for me is actually the awkward screen model. I can imagine things going well on a single ginormous screen, and if I was running on one of the 27" iMacs, there'd be no problem. The trouble comes when you have multiple monitors, because the way xmonad seems to track them is by assigning a different "workspace" to each monitor. I'm sure this fit the program model perfectly, but it means that Alt-Tab only cycles between open windows on whichever monitor you have focus, and you have to pick your "focused" monitor. It's possible that I'm spoiled and this is actually how most TWMs work, but Stump doesn't seem to treat windows on different physical screens as separate areas, and I don't need to pick a working monitor. The other issue it brings up is with workspace switching. Because Bluetile gives you 9 workspaces (and assigns 1 to your first monitor, and 2 to your second), you need to be careful about which you switch to lest you screw yourself. For example, if you open Emacs on one monitor and a browser on another, then switch to workspace 2, they switch places. That is, your Emacs window gets shunted to monitor 2 while your browser gets pulled to the one you were looking at. That's not really what I want if I have multiple screens staring at me. If you then switch to workspace 4 (lets say you have Movie Player open there), your Emacs window stays where it is and workspace 4 replaces your browser in monitor 1. Now, moving back to workspace 1 causes your Emacs window to fly back onto monitor 1 and Movie Player to go to monitor 2. In other words, you're technically back where you started, except that workspace 2 now contains Movie Player instead of your browser. How do you get back to your initial setup? You have to switch to workspace 2 then to workspace 4 then back to workspace 1. This leaves something to be desired; and demonstrates that by conflating "monitors" and "workspaces", grater user-side complexity is achieved with no visible upside.

Treating monitors this way also introduces an extra level of complexity in the UI; you also need keys to select your primary monitor (they're Win-w, Win-e and Win-r in Bluetile; I don't know what happens if you have more than three monitors). That's too much to keep in my head, and this is coming from someone who uses Emacs. I won't be switching to Bluetile any time soon, and their docs give the impresion that this was pretty much how xmonad handles things too, which is sad. And means I'm sticking with Stump for the forseeable future.

1 [back] - So you don't so much have to memorize them as come up with some simple mnemonics and then assign keys to match those. For example, my .stumpwmrc is set so that C-[keystroke] starts up programs, C-M-[keystroke] runs a work-related shortcut (such as remote desktop, or opening my timesheet file) and M-[keystroke] does wm-related tasks. [keystroke] is typically just the first letter of whatever I'm trying to do (so C-e runs Emacs and C-M-r runs Remote Desktop). This is a mnemonic that makes sense for my workflow. I could easily have just kept track of my most common tasks and bound each to an F key.

2 [back] - For example, if you need to do some drawing. Either of decorative pieces/icon modifications for a web app or for the UI layouts in an environment like Flash/VB. In this situation, it goes without saying that you actually want a tablet, or a trackball, or a multi-touch trackpad, as opposed to a vanilla mouse. The only thing I'd use the traditional option for these days is gaming, and even then, tablets give you an edge if you know what you're doing because of the 1:1 mapping of screen to tablet.

Before I go any further, as an aside, the irony of a guy who writes a blog called "Language Agnostic" going to something called the "Dynamic Languages Smackdown" is not lost on me. It turns out I wasn't the only language nerd there though, and if nothing else I got a new book recommendation out of it.

The seven languages were Smalltalk, Ruby, Python, Erlang, Lisp, JavaScript and Perl, and the format was

Introduction

Questions from the audience

Questions

Code examples

To summarize, I kicked off (subtly, so no one seems to blame me yet) a line of questioning dealing with canonical implementations that we kept coming back to throughout the talk. Andrey Paramonov had it easy, because Erlang actually has just one canonical implementation (with one attempted port to the JVM that apparently no one takes seriously yet). Other than Erlang, what struck me here is how diverse the pool actually is. I mostly hack Common Lisp these days, and only vigorously play with Ruby, Erlang and Haskell (and PHP at work, but as you can see by the logo bar, I'm not terribly proud of that), so I was under the impression that Lisp was the only freak language that had so many implementations to choose from[1]. That turned out to be a misconception; Ruby has JRuby and Iron Ruby (both of which purportedly conform to the same spec and are both interchangeable and "official" as far as the community is concerned), Myles Braithwaite put up a slide listing twenty or so different Python implementations (which variously support Python 2.5, 2.9 and 3.x specs), Smalltalk has at least two open-source forks (and gnu-smalltalk, but that wasn't really discussed), the Perl community is apparently split between 5 and 6 and Javascript has at least three different server-side implementations (the client-side situation is worse).

It's weird, because as I've said, I was under the impression that "a language" meant one canonical implementation with one or two experimental projects, but (at least in the dynamic world) that seems to be false. It's odd, because people cite "difficulty choosing an implementation" as one of the principal reasons not to go with Common Lisp. I guess it's more of an excuse afterall.

The other big surprise was the age of the advocates. Of the seven, only Alan Rocker (the Perlmonger of the group) had the sort of beard you'd expect, and everyone other than Alan and Yanni (the Smalltalk presenter) seemed to be a student. I'm particularly happy about this since Lisp gets cast as the old-man's language, but in reality, programmers my age seem to be more common. Not that "age of the community" is important in any tangible way, just interesting.

"Smackdown" thankfully turned out to be too strong a word; other than a fierce rivalry between the Python and Ruby presenters (and a few low-blows from both of them aimed at JavaScript), everyone was respectful of the other languages there. It was fairly informative, and I'm going to pick up and play with Clojure, a Smalltalk (either gnu or Pharo) and more Python as a direct result.

A note for future presentations in this vein though:

Please don't do code examples last. This should have been done up-front with the introductions, and probably alotted 15 minutes or so per language. Alan didn't even get enough time to present his.

Either admit that these discussions will take more than two hours, or invite fewer languages at once. The conversations easily could have continued for a further hour or two (and probably did at the pub after the event, but I had work the next day, so I couldn't go).

Be prepared with the slides beforehand (anyone else would be able to blame PowerPoint, but this was the Linux User Group, so you don't get that luxury).

Preliminary Impressions of Smalltalk

I did briefly try to get into Pharo this morning, but I found it annoying to say the least. This doesn't mean I won't keep trying; I had a negative initial reaction to pretty much every language I currently know and love. There are some definite initial concerns though, the biggest of which is that Pharo insists that you use its "Environment" (which is only really a big deal because of the way that environment is constructed). It's heavily mouse-dependant (in fact the intro text suggests you get yourself a three-button mouse with a scroll-wheel to get the most out of it), and it insists on handling its own windowing (which means if you got used to a tilingwindowmanager, you are so screwed). The gnu implementation is titled "The Smalltalk for those who can type", so at least I know I'm not alone. Minor concerns about image-based development include things like "How does source control work?" and "how do I use Pharo on a team?", but I'm sure those are resolved and I simply haven't dug deeply enough to have an idea of how yet.

1 [back] - First off, the "language" is split into Scheme, Common Lisp, and Other. In the Scheme corner, you have Racket (formerly PLT), Guile, Termite (which runs on top of Gambit), Bigloo, Kawa and SISC (and a bunch of smaller ones). In Common Lisp, there's SBCL, CMUCL, Clisp, Armed Bear and LispWorks (and about 10 smaller ones). Finally in "Other", you find crazy things like Emacs Lisp, AutoLisp, Arc, Clojure and newLisp (which are all technically Lisps, but conform to neither the Common Lisp nor Scheme standards). This is why I think having a representative for "Lisp" is a joke at a talk like this; which Lisp are you talking about?

Ruby and Erlang each come with their own modes, and recent Emacs versions ship with a built-in Python mode and shell. Smalltalk uses its own environment (though GNU Smalltalk does have its own mode), and I'd really rather not talk about PHP. If you're writing in it, chances are you're using Eclipse or an IDE anyway.